Access Cavity Preparation 1

7/30/2019 Access Cavity Preparation 1

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Mandibular first premolar

Overall tooth length- 22.5mm Average crown length- 8.5mm

Average root length- 14mm

External root morphology:-

Single rooted

Buccolingually Wider

Mesiodistally Narrower

Developmental depressions or grooves- mesial anddistal surface of root


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Root number and canal systems:-

Single rooted with single canal

High failure rate of RCT 11.4% because of the numerous

variations in root canal morphology

Buccal canal has straight line access

Lingual canalbranches are at sharp angle


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Variations and Anaomalies

Number of roots

Number of canal and apices

No. ofstudies

No. ofteeth

One root Two root Threeroot

Four root

8 4462 97.9% 1.8% 0.2%


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3 rooted mandibular 1st premolar

mandibular 1st premolarI root and 3 canals


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Mandibular left premolar with 3 canal and 2 roots


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Anatomy and morphology

Sharp buccal cusp

Small lingual cusp- resembles cingulum

Occlusal view

Outline: diamond shaped

Crown is lingually placed


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Mandibular second premolar

Overall length 22.5mm

Average crown length - 8mm

Average root length - 14.5mm

External root morphology:-

Single rooted

Mesial surfaceflat or convex

Distal surface- longitudinal developmental depression


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Number of roots and canal systems:- Single rooted with single canal


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Variations and anomalies

Number of roots

Number of canal and apices

Number ofstudies

Number ofteeth

One root Two roots Three roots

8 4019 99.6% 0.3% 0.1%

Number

of studies

Number

of teeth

One canal Two or

morecanal

One canal

at apex

Two or

morecanal atapex

10 2983 91.1% 8.9%

7 1970 91.6% 8.4%


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Premolar exhibiting dens evaginatus

One root two root canals


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Mandibular right 2nd premolar with 2canals and one apical foramen

2nd premolar with hypertaurodontmesial and distal root


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Mandibular left 2nd premolar with 2 roots and 3 canals


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Anatomy and morphology:-

Has two forms from occlusal aspect:

3 cusp type (most common)

2 cusp type


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Access preparation of mandibular

premolar teeth1) Entrance through occlusal surface

Initial preparation

center of center groove and the bur is directed parallelto the long axis of the tooth


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2) No. 4 round bur is used to open into the pulp

chamber

In removing the bur, the occlusal opening is widened

buccolingually to twice the width of the bur


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3) Endodontic explorer is used to locate the central

canal

Tension of the explorer against the walls of

preparation will indicate the amount and direction of

extension


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4) Working from inside the pulp chamber to outside,

no.2 or 4 round bur is used to extend the cavity buccolingually by removing the roof

of the pulp chamber


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5) 702 U fissure bur is used for buccolingual extension

and finish of cavity walls


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6) Final ovoid preparation is a tapered funnel from the

occlusal to the canal, providing unobstructed access

to the canal


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7) Occlusal view of final access opening

Anatomy of pulp chamber ---ovoid buccolingually


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Mandibular 1st molar

Overall length -21.5mm Average crown length -7.5mm

Average root length -14mm

External root morphology

Two rooted teeth

Mesial and distal

Broader buccolingually than mesiodistally


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Number of roots and canal systems

Two roots with three or four canals


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Number of roots

Number of canals and apices

No. ofstudies

No. ofteeth

One root Two roots Threeroots

Fourroots

10 3263 - 96.9% 2.97% -

No. ofcanals

andapices

No. ofstudies

Numberteeth

Onecanal

2 ormore

Onecanal at

apex

Two ormore

canals atapex

Mesial 16 3375 4.2% 95.85

13 1731 46.3% 53.7%

distal 15 3304 68.3% 31.7%

13 1805 82.4% 17.6%


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Anomalies

Mandibular 1st molar with 3 roots (M, D, DL) and four canal systems


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Mandibular right 1st molar exhibiting mesotaurodontism


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Buccal cusp tips are located more to the midline on

occlusal table compared to lingual cusp tips


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Mandibular 2nd molar Overall length-20mm

Average crown length-7mm

Average root length-13mm

External root morphology:- Two rooted

Mesial and distal ( most frequently fused)

Broader buccolingually than mesiodistally

Root convcavities Mesial surfaces of both roots

Distal surface of mesial root


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Number of roots

Number of canals and apices

No. ofstudies

No. ofteeth

Incidence offusedroot

One root(conical)

One root( c-shaped)

Tworoots

Threeroots

9 997 21.8% - - 96.9% 2.97%

6 674 8.3% 8.5%

No. ofcanals

andapices

No. ofstudies

Numberteeth

Onecanal

2 ormore

Onecanal at

apex

Two ormore

canals atapex

Mesial 8 1194 14% 86%

7 778 60.3% 39.7%

distal 8 1194 85.1% 14.9%

7 778 95% 5%


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Number of roots and canal systems

Two roots with three canals


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Fused roots

One root one root canal


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Mandibular left 2nd molar 2 mesial rootand 1 distal root(3 canal systems)

Mandibular right 2nd molar with 2roots and

2 root canals


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Occlusal tablemore symmetrical and rectangular

with four cusps

roots are inclined more distally in relation to occlusal

table


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Access preparation of mandibular

molars1) INITIAL EXTERNAL OUTLINE FORM Staring location is on the central groove way between

mesial and distal boundaries

Bur is directed prependicular to the occlusal table


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2) PENETRATION OF THE PULP CHAMBER

ROOF

No. 4 or 6 round bur is used to open into pulp chamber

Bur should be directed towards the orifices

of the mesiobuccal or distal canal ,where the

greatest space in the chamber exists


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3) An endodontic explorer is used to locate the

orifices of the distal, mesiobuccal and mesiolingual

canals.

Orifices of the canal forms theperimeterof the preparation


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4)Complete roof removal

Goal funnel the corners of the access cavity directly

into the orifices

Round bur hooks under the lip of the pulp horn


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The safety tip diamond or carbide bur is passed

between the orifices along the axial wall to taper the

internal wall


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5) Removal of cervical dentin bulges and coronal

and orifice flaring

Cervial bulges are removed with gates glidden drill

Constricted coronal portion flared with GG drill used insweeping upward motion with lateral pressure away from

furcation


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6) Finally the canals should have a straight line of

access

Leaning the entire preperation towards the mesial

improve ease of access

Walls should be perfectly smooth and

orifices located at exact pulpal-axial angle

of cavity floor


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7) Anatomy of the pulp chamber

trapezoidal

Both mesial and distal walls slope mesially

Documents

Access Cavity Preparation 1